1. Field of the Invention
The present invention relates to a drive circuit for an insulated gate semiconductor element.
2. Description of the Background Art
In gate drive control for an Si semiconductor element, generally, a source potential and a gate potential are made equal to each other at a turn-off.
In an insulated gate switching element, such as a SiC-MOS, which has a low threshold voltage Vth, however, when a source potential and a gate potential are equal to each other at a turn-off, there is a possibility that the insulated gate switching element may wrongly turn on by a slight increase in the output voltage of a drive circuit at a power-on.
Then, in Patent Document 1 (Japanese Patent Application Laid Open Gazette No. 8-298786), for example, disclosed is a configuration in which a negative bias is applied to a control terminal of a switching element and the control terminal becomes a negative potential as viewed from a main terminal at a turn-off, to thereby prevent the wrong ON.
When a power supply voltage of the drive circuit for the switching element rises earlier than the negative bias power supply at a power-on, however, since no negative bias is applied to the control terminal of the switching element at the instant, there is a problem that the switching element wrongly turns on when an output voltage of the drive circuit exceeds a threshold voltage of the switching element.